Manufacturing Quality Investigation of EPS Blocks with Homogenous Test Lee-kuo Lin Associate Professor Civil Engineering Department National Taipei University of Technology, lklin@ntut.edu.tw Taipei City ,Taiwan, R.O.C Kenji Sasaki Manager of Overseas Marketing Project Team SEKISUI PLASTICS CO, LTD Tokyo City , Japan Shang-Juin Chiou3 Graduate Student Civil Engineering Department National Taipei University of Technology Taipei City ,Taiwan, R.O.C ABSTRACT EPS light-weight embankment method is a kind of construction method which uses EPS blocks to stack up as a geofoam embankment EPS blocks are made from styrene particles through a process of foaming, pressurizing and heating If the quality of EPS block production is not good enough, damage to the EPS block will occur due to un-uniform deformation Therefore, if using poor quality of EPS blocks as the road sub-grade embankment, it will have a serious problem This study focuses on EPS block productions in Taiwan and Japan to uniformity analysis and comparison Because Japan has considerable experience in EPS technology, so in this study, Japanese EPS block would be the object of comparison to understand the difference of the quality between Taiwan and Japan EPS manufacturing In the study two 20kg/m3 (20K) EPS blocks with dimension of 2m×1m×0.5m were shipped from Japan to Taiwan, and homogenous test specimens were made from these two samples The same testing process is used for Taiwanese EPS samples After comparison and analysis of the measured data, uniformity quality of EPS productions is fed back to those Japanese and Taiwanese manufacture firms Keywords：EPS, geofoam, manufacturing, homogenous, uniformity test I PREFACE Taiwan has a harsh natural environment and high population density In recently years, the cost of living in urban areas has increased, and people move to develop suburban or mountain areas Taiwan is located at the Circum-Pacific seismic zone with a sub-tropical humid climate Due to this situation Taiwan is a country with the most frequent earthquakes in the world [1] Also due to the high annual rainfall, landslides or debris-flows frequently occur After the 921 Gigi earthquake which happened in 1999, mountains in Taiwan generally have a potential hazard for avalanches and falling rocks initiating debris flow disasters Due to the number of natural disasters, Taiwan urgently needed to develop a better disaster prevention system than other countries EPS is the generic abbreviation of Expanded Polystyrene, produced by refining liquid-monomer styrene from petroleum, re-synthesized to solid polystyrene beads and molded into EPS blocks by heating in pressurized molding form, [2, 3] Because EPS, also called Geofoam, has characteristics, such as light weight, impact absorption, self-supporting, water resistance, temperature insulation, easy construction and other features [1, 4], it is often used to replace the embankment material in civil engineering projects (Figure 1) Figure EPS embankment in Taiwan EPS lightweight embankment method is one kind of construction method where EPS blocks are stacked up to form an embankment If the quality of the EPS block production is not satisfactory, there will be problems with inhomogeneous foam particles that may cause damage to EPS blocks when subjected to traffic and other loads (Figure 2) This study focuses on EPS block production in Taiwan and Japan to uniformity analysis and comparison and report the experimental result to the EPS suppliers Because there is considerable experience with EPS technology in Japan, two 20 kg/m3 EPS blocks supplied from the Sekisui Plastics Company will be used as comparison objects for this study It is envisaged that the result of this research that can promote the quality of EPS manufacturing and disaster prevention in the domestic construction industry and engineering applications in Taiwan Figure Road damaged due to poor EPS quality II EPS MAUNFACTURING PROCESS Polymer plastic raw materials are extracted from crude oil distillation and oil/gas separation process mainly EPS is one of its derivatives The refining process produces 96% of products that are supplied to fuel consuming vehicles and machines The plastics material derived from the refining process accounts for about 4% of products, and EPS products accounts for only 0.1% (Figure 3) In Taiwan, a block of EPS is made from particles of polystyrene (PS) being expanded and melted in an automatic molding process by adding steam Expanded polystyrene is created during a two-stage process In the first stage, expandable polystyrene resin is pre-expanded by a hydrocarbon-blowing agent that is contained within tiny resin beads When the beads are exposed to steam, the polymer softens and the blowing agent expands, creating a cellular structure within the "pre-puff" beads (Figure 4)[5] After a short stabilization period, the pre-puff is placed in a large rectangular block mold and steam is injected into the mold Under such heat and pressure, the beads further expand and fuse to form a molded block [3](Figure 5) The result is a white, synthetic material that has a texture of closed, gas filled cells Individual cells, or beads, are still visible after the molding process, but the beads have coalesced, to form a closed fabric, with essentially no void between the cells [2] (Figure 6) The process can be done by an EPS manufacturer There are 18 EPS manufacturers in Taiwan In this research of those EPS manufacturers were visited The complete manufacturing process is as shown in Figure Figure Crude oil refining process and product [6] (b) Optical microscope picture of EPS pre-puff beads Figure Pictures of PS and EPS Beads (a) Beads of PS and EPS PolyStyrene Raw Material Second Matured and Dried First Expanded First Matured and Dried Second Expanded Figure EPS expended process [6] Figure Optical microscope picture of EPS Mold Produing EPS Block Figure The flow chart of EPS manufacture In Japan, the first step of the EPS production process is to foam the PS particle once, foaming rate is times to 100 times The product is then placed at a silo for one day After that, the expanded beads are feed into a molding machine to foam an EPS block by high temperature and high pressure [7] The manufacturing process is shown in Figure After molding EPS blocks with printed block on number and date of production are put into a drying room for days The weight and size are then measured, randomly sampling of / 100 individuals After cutting compression strength tests and fire test are performed to confirm the quality before blocks are transferred to a shipping warehouse Japanese EPS blocks have special markings for blocks meeting the quality standard set by the EPS development institution EDO Figure shows a label for Japanese EPS blocks used in engineering backfill applications, the EPS block has been marked with an exclusive sign Close mold , Close mold, Filled with air foam bloeback Filling tube or Machine residual foam particles back into the hopper Mold heating Steam pipe to remove water in the mold and raise the temperatur e Heating Through the steam to promote the integration of secondary foam Behind sides heating Two sides heating Exhaust Water cooling Promote the product surface extension Pressure release Make mold cooling Vacuum cooling Making water to evaporate , the foam pressure drop down Separated from the mold pressurized air , so that products from the mold release Eject Using EJECT PIN to remove products after extrusion Figure EPS block manufacturing flow chart in Japan Figure Japanese quality certification of EPS block The material characteristics of EPS include the following [5, 7, 8]: (1) Lightweight: the density of EPS is only 1/100 of sand, and may be supported even by soft subsoil foundations (2) Economical: short construction time, space saving, less excavation, low maintenance and lower total cost (3) Easy for construction: large machines are not needed only manpower is required (4) Self-supporting: low Poisson ratio, high self-supporting can reduce lateral soil pressure, suitable for use in construction of retaining backfill material (5) Excellent impact absorption: EPS provides less impact and shock effect (6) Water resistance: high resistance to water absorption and not easily distorted The material characteristics of EPS can be used in many ways of engineering applications and it can become a substitute for sand as a backfill material [9] III HOMOGENOUS TEST OF EPS BLOCKS The concept of EPS homogenous test was launched by the first author in 2010 [5] For the testing process, the first step is to cut the EPS block into cubes of 10cm×10cm×10cm then tag a number on each cube specimen In this research, the main experiment divides into uniformity test of EPS specimens, physical properties test and impacting test Physical properties test include compressive strength, water absorption and hardness The main purpose of the experiment is to compare the quality of EPS production in Taiwan and Japan, then provide Taiwan’s EPS manufacturers with the result in order to improve the quality control of their processes In this research, the testing process is shown in Figure 10 Figure 10 Experimental flow chart VI EPS BLOCK PREPARING AND CUTTING PROCESSES The length, width and height of all EPS blocks were measured The result is shown in Table Then each block was cut into 10cm x 10cm x10cm cubes, and marked with alphabetical letters on each side (Table 2) Such coding marked on the specimen is used for identification and analysis after the measurement Table Size of test materials Table Code of materials The preparation and cutting steps are explained below: Mark the relative position between EPS block and mold in the manufacture firm Measure dimensions of EPS block, including length width and height, then measure the weight of the entire EPS block From the recorded data calculate its unit weight (K value) In accordance with EPS blocks’ length, width and height planned to cut the size of each side, using ruler to draw the cutting line on each plane, then marked A1, A2, A3….etc in sequence on the first cutting surface After having marked with number, put the first cutting surface on the cutter sequentially cutting into cube specimens with sides 10 cm Similar to step and step 4, marked and cut B1, B2 , B3….etc in sequence on the second cutting surface Repeat step to step 6, until all specimens are cut completely V HOMOGENOUS TEST AND ANALYSIS The object is to identify how homogenous the EPS block is after being foamed This can avoid that engineering damage happen due to internal defects in EPS material used as an embankment fill material If the EPS production process has good and uniform quality, the unit weight (K value) of EPS block before cutting should be the same as the 10 cm small cube specimens after cutting If it has different result, it will mean that there is a non-uniform problem in the EPS molding process In this study, tools of electronic scale and cursor caliper are used to measure every cube’s weight and volume According to the EPS suppliers’ specification, the standard of unit weight is 0.2kN/m3(+0.015/-0.01) Table3 shows the measured result of unit weight with Japanese EPS and Table4 shows part of the Taiwanese result Table Part of measured result of unit weight with Japanese specimens Weight Length Wide Height Volume Unit Difference Number 3 (g) (cm) (cm) (cm) (cm ) weight(kN/m ) (+0.015/-0.01) C2-20 C9-20 G2-20 H2-20 H3-20 H5-20 H9-20 I10-12 I10-13 I10-14 17.88 18.19 18.8 18.77 18.54 18.84 18.38 19.78 20.02 20.01 9.846 9.889 9.923 9.854 9.858 9.866 9.873 9.075 9.117 9.017 8.209 9.809 9.994 9.837 8.403 9.828 8.442 9.873 9.861 9.853 9.874 8.342 8.448 8.359 9.827 8.462 9.815 9.883 9.868 9.888 798.07 809.18 837.79 810.26 814.03 820.50 818.05 885.49 887.16 878.49 0.219 0.220 0.219 0.227 0.223 0.225 0.220 0.218 0.221 0.223 +0.019 +0.020 +0.019 +0.027 +0.023 +0.025 +0.020 +0.018 +0.021 +0.023 Table Part of measured result of unit weight with Taiwanese specimens Number Weight (g) Length (cm) Wide (cm) Height (cm) Volume (cm3) Unit weight(kN/m3) Difference (+0.015/-0.01) K1-18 K10-18 O1-1 O6-6 O6-8 O6-9 O6-10 O10-1 22.03 22.25 21.87 19.01 18.95 18.66 18.94 21.78 9.994 10.061 9.927 9.847 9.85 9.895 9.849 9.895 9.848 9.928 10.152 10.124 10.116 10.109 10.117 10.1 10.119 10.148 9.882 9.895 9.877 9.891 9.88 9.903 995.92 1013.63 995.89 986.44 984.17 989.38 984.46 989.70 0.216 0.215 0.215 0.188 0.188 0.184 0.188 0.215 +0.016 +0.015 +0.015 -0.011 -0.011 -0.015 -0.011 +0.015 VI CONCLUSIONS Two Japanese EPS blocks were cut into 2000 cubes and had 10 cubes not complying with the standard The location of the failed cubes is shown in Figure and Figure 10 These 10 specimens not meet specifications, but all of these have higher unit weights than 0.215 kN/m3 Two Taiwanese EPS blocks were cut into 1080 cubes and had 557 cubes not complying with the standard There are cubes with densities lower than 0.199kN/m3 (Figure 11) The testing result shows that homogeneity quality of Taiwanese EPS blocks qualification rate is only about 48% Figure Japanese D-20 (1) locations of Figure 10 Japanese D-20 (2) locations of failure failure Figure 11 Taiwanese D-20 locations of failure Based on this study, homogeneity of the Japanese EPS is up to 99.5% passing rate, 10 failures of the unit weight was higher than 0.215 kN/m3 Taiwan has only 48.4% passing rate The study result shows that Taiwan EPS manufacture quality still needs to be improved This study uses heated 0.3mm Nickel-chromium wire to cut EPS specimens, Table shows the consumption rate of Taiwanese and Japanese EPS blocks The consumption rate of Taiwan is up to 27.51% because the size of Taiwanese EPS blocks is 184cm×101cm×67cm, but this study needs 10cm×10cm×10cm cube specimen, so Taiwanese EPS blocks can just be cut to 180cm×100cm×60cm Therefore the consumption rate will be high Table Consumption rate of cutting procedure Test materials Weight(kg) Total of specimens weight(kg) Japan D-20(1) 20.68 19.49 Japan D-20(2) 20.58 19.35 Taiwan 20K 26.69 23.44 Consumption (%) 5.74% 5.98% 27.51% VII REFERENCES Lin Lee-kuo, The Supplying Condition of Aggregate and Application of EPS Construction Method in Taiwan Proceedings of Conference on New Technique in Geotechnical Engineering Taiwan, R.O.C p.1-17, 1998 Bartlett S Design of Geofoam Embankment for the I-15 Reconstruction Proceedings of the Technique Conference of EPS Construction p.10-1-10-10, 2000 Negussey D Properties and applications of Geofoam Society of the Plastics Industry, Washington, D.C., 1997 Frydenlund TE and Aaboe R Expanded Polystyrene -The Light Solution Proceedings of the International Symposium on EPS Construction Method, Tokyo, JP p.383-388, 1996 Lin Lee-kuo, Ch Li-hsie and Roger H L Chen, 2010.02, “ Evaluation of Geofoam as a Geotechnical Construction Material”, ASCE Journal of Materials in Civil Engineering, Volume 22, Issue 2, 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13 Horvath JS Geofoam Geosynthetic Horvath Engineering PC Scarsdale, NY, 1995 14 Norwegian Road Research Laboratory Expanded Polystyrene Used in Road Embankments: Design, Construction and Quality Assurance Form 482E Oslo 1992 10 ... Design of Geofoam Embankment for the I-15 Reconstruction Proceedings of the Technique Conference of EPS Construction p.1 0-1 -1 0-1 0, 2000 Negussey D Properties and applications of Geofoam Society of. .. weight with Japanese specimens Weight Length Wide Height Volume Unit Difference Number 3 (g) (cm) (cm) (cm) (cm ) weight(kN/m ) (+0.015 /-0 .01) C 2-2 0 C 9-2 0 G 2-2 0 H 2-2 0 H 3-2 0 H 5-2 0 H 9-2 0 I1 0-1 2 I1 0-1 3... characteristics of EPS can be used in many ways of engineering applications and it can become a substitute for sand as a backfill material [9] III HOMOGENOUS TEST OF EPS BLOCKS The concept of EPS homogenous